Advice on connecting meshes
Found a way to do it, scale out the top of the circle select the vertices from 10 to 2 o'clock then S Y 0 then extrude the straight edge to the adjacent edge of the mesh.

Repeat for the Vertices from 8 to 4 O'clock locations. 

Add Loop cuts and joining up the vertices using the magnet tool, select all and press W and click on remove doubles.